Modern data processing systems commonly consist of a plurality of separate components such as processors, memory boards, input/output controllers, data storage devices and peripheral devices or terminals. Signals are transmitted between these components via a common bus. As computer systems become more complex, there is a continuing requirement for driving signals at faster clock rates while at the same time minimizing power, noise, and electro-magnetic interference. In order to avoid the inherent problems of electrically coupling data processing components, attention has shifted to optical techniques for data transmission.
Representative is U.S. Pat. No. 4,732,466, which employs a circuit board having an optical data bus. In this system each component includes an optical fiber network which in a composite sense forms an optical bus to interconnect computer components on the same board. The intensity of light emitted by a component is divided among various receivers so that the optical energy arriving at each receiver is reduced. If components are interconnected consecutively in a chain-like manner, each linked component receives significantly less intensity than the preceding one. Consequently this optical bus does not assure optical power uniformity, which is an essential requirement in digital data transmission.
Other techniques have been proposed in the art for using optical couplers for data transmission. U.S. Pat. No. 4,400,054 relates to an optical coupler used to transmit data from any one of N small optical channels by funneling to a single "large" optical channel. This technique does not provide an optical interconnection scheme for purposes of computer bus applications where all optical ports must be interconnected to allow bidirectional communication between any two devices.
A specific system for optical signal transmission is described in U.S. application Ser. No. 654,472 now U.S. Pat. No. 5,131,061. Modular fiber optic couplers are combined to form a bus structure in a fiber optic environment. Each coupler unit comprises optical and electrical input and output ports. Optical receivers and transmitters are connected to the optical ports and linked with the respective electrical ports by means of electronic logic control elements which are an integral part of each coupler unit. By interconnecting the electrical ports of several couplers in a network like structure, individual components linked by the optical bus can be addressed. During data receiving periods, however, no data can be sent from the same device simultaneously. Another disadvantage is the need of additional supply power and the respective interconnection parts as there are active electronic elements integrated on each coupler unit.
The present invention is intended to provide a new and advanced optical data distribution system using specific couplers or modules to realize complex optical bus structures or networks which allow selective and parallel data transfer among a plurality of devices.